override protected void DispatchNode(Node node, object data)
{
if (IsAlreadyVisited(node))
{
return;
}
AddAlreadyVisited(node);
handler(node);
for (int i = 0; i < node.NextArray.Count; i++)
{
AddTask(node.NextArray[i], null);
}
UserFilteredBlock userFilteredBlock = node as UserFilteredBlock;
if (userFilteredBlock != null)
{
AddTask(userFilteredBlock.Filter, null);
}
ProtectedBlock protectedBlock = node as ProtectedBlock;
if (protectedBlock != null)
{
for (int i = 0; i < protectedBlock.Count; i++)
{
AddTask(protectedBlock[i], null); //Handlers
}
}
}
/// <inheritdoc />
public BasicBlock <TInstruction> GetLastBlock()
{
BasicBlock <TInstruction> result = null;
for (int i = Handlers.Count - 1; i > 0 && result is null; i--)
{
result = Handlers[i].GetFirstBlock();
}
return(result ?? ProtectedBlock.GetLastBlock());
}
/// <inheritdoc />
public BasicBlock <TInstruction> GetFirstBlock()
{
var result = ProtectedBlock.GetFirstBlock();
for (int i = 0; i < Handlers.Count && result is null; i++)
{
result = Handlers[i].GetFirstBlock();
}
return(result);
}
protected internal override void VisitProtectedBlock(ProtectedBlock node, object data)
{
StackTypes stack = data as StackTypes;
if (stack.Count != 0)
{
throw new VerifierException();
}
foreach (EHBlock block in node)
{
AddTask(block, new StackTypes());
}
AddTask(node.Next, stack);
}
/// <inheritdoc />
public IEnumerable <BasicBlock <TInstruction> > GetAllBlocks()
{
foreach (var block in ProtectedBlock.GetAllBlocks())
{
yield return(block);
}
foreach (var handler in Handlers)
{
foreach (var block in handler.GetAllBlocks())
{
yield return(block);
}
}
}
private void HandleException(Node node, Exception exc)
{
// Searching appropriate handler
Type excType = exc.GetType();
EHBlock handler = null;
Block parent = node.Parent;
while (!(parent is MethodBodyBlock))
{
if (parent is ProtectedBlock)
{
ProtectedBlock tryBlock = parent as ProtectedBlock;
for (int count = 0; count < tryBlock.Count && handler == null; count++)
{
if (tryBlock[count] is CatchBlock)
{
CatchBlock catchBlock = tryBlock[count] as CatchBlock;
if (catchBlock.Type.IsAssignableFrom(excType))
{
handler = catchBlock;
}
}
}
}
parent = parent.Parent;
}
if (handler == null)
{
unhandledException = exc;
}
else
{
state.Stack.Clear();
state.Stack.Push(new ObjectReferenceValue(exc));
AddTask(handler);
}
}
private void EmitProtectedBlockTable()
{
List<ProtectedBlock> entries = new List<ProtectedBlock>();
foreach (var clause in MethodCompiler.Method.ExceptionBlocks)
{
ProtectedBlock prev = new ProtectedBlock();
foreach (BasicBlock block in exceptionBlocks[clause])
{
uint start = (uint)codeEmitter.GetPosition(block.Label);
uint end = (uint)codeEmitter.GetPosition(block.Label + 0x0F000000);
ExceptionHandlerType kind = clause.HandlerType;
uint handler = 0;
uint filter = 0;
MosaType type = clause.Type;
handler = (uint)codeEmitter.GetPosition(clause.HandlerOffset);
if (kind == ExceptionHandlerType.Filter)
{
filter = (uint)codeEmitter.GetPosition(clause.FilterOffset.Value);
}
// TODO: Optimization - Search for existing exception protected region (before or after) to merge the current block
// Simple optimization assuming blocks are somewhat sorted by position
if (prev.End == start && prev.Kind == kind && prev.Handler == handler && prev.Filter == filter && prev.Type == type)
{
// merge protected blocks sequence
prev.End = end;
}
else if (prev.Start == end && prev.Kind == kind && prev.Handler == handler && prev.Filter == filter && prev.Type == type)
{
// merge protected blocks sequence
prev.Start = start;
}
else
{
// new protection block sequence
ProtectedBlock entry = new ProtectedBlock(start, end, handler, kind, type, filter);
entries.Add(entry);
prev = entry;
}
}
}
int tableSize = (entries.Count * NativePointerSize * 5) + NativePointerSize;
string section = MethodCompiler.Method.FullName + @"$etable";
using (Stream stream = MethodCompiler.Linker.Allocate(section, SectionKind.ROData, tableSize, NativePointerAlignment))
{
using (EndianAwareBinaryWriter writer = new EndianAwareBinaryWriter(stream, Architecture.Endianness))
{
foreach (ProtectedBlock entry in entries)
{
// FIXME: Assumes x86 platform
writer.Write((uint)entry.Kind);
writer.Write(entry.Start);
writer.Write(entry.Length);
writer.Write(entry.Handler);
if (entry.Kind == ExceptionHandlerType.Exception)
{
// Store method table pointer of the exception object type
// The VES exception runtime will uses this to compare exception object types
MethodCompiler.Linker.Link(LinkType.AbsoluteAddress | LinkType.I4, BuiltInPatch.I4, section, (int)writer.Position, 0, entry.Type.FullName + "$mtable", 0);
writer.Position += NativePointerSize;
}
else if (entry.Kind == ExceptionHandlerType.Filter)
{
// TODO: There are no plans in the short term to support filtered exception clause as C# does not use them
writer.Position += NativePointerSize;
}
else
{
writer.Position += NativePointerSize;
}
}
// Mark end of table
writer.Position += TypeLayout.NativePointerSize;
}
}
}
protected override void VisitProtectedBlock(ProtectedBlock node, object data)
{
result = false;
}
protected override void VisitProtectedBlock(ProtectedBlock node, object data)
{
AddTask(node.Next);
}
protected internal virtual void VisitProtectedBlock(ProtectedBlock node, object data)
{
throw new NodeNotSupportedException(node);
}
public static MethodBodyBlock Convert(MethodEx method)
{
if (!method.IsVerified)
{
throw new ConvertionException();
}
MethodInfoExtention _method_ = new MethodInfoExtention(method.Method);
MethodBodyBlock mainBlock = new MethodBodyBlock(_method_.GetReturnType().type);
mainBlock.Options["StackTypes"] = new StackTypes();
Block currentBlock = mainBlock;
Node[] heads = new Node[method.Count];
Node[] tails = new Node[method.Count];
Node head = null;
Node tail = null;
Node firstBlock = null;
Node lastBlock = null;
int iNum, iNumNext;
Variable[] locals = new Variable[method.Locals.Count];
Variable[] args = new Variable[_method_.ArgCount];
VariablesList methodVarList = mainBlock.Variables;
for (int i = 0; i < args.Length; i++)
{
args[i] = methodVarList.CreateVar(_method_.GetArgType(i).type, VariableKind.Parameter);
args[i].Name = "Arg" + i;
// methodVarList.Add(args[i]);
}
for (int i = 0; i < locals.Length; i++)
{
locals[i] = methodVarList.CreateVar(method.Locals[i], VariableKind.Local);
locals[i].Name = "Loc" + i;
// methodVarList.Add(locals[i]);
}
BlockType nextBlockType;
int nextBlockStart = -1;
int nextBlockEnd = 1 << 30;
int nextBlockIndex;
Type nextCatchBlockType;
Hashtable tryBlocks = new Hashtable();
Hashtable filterBlocks = new Hashtable();
Stack blockEnds = new Stack();
blockEnds.Push(method.Count);
FindNextBlockStart(method.EHClauses, out nextBlockType, ref nextBlockStart, ref nextBlockEnd, out nextCatchBlockType, out nextBlockIndex);
//Nodes and blocks creation, blocks linkage
for (iNum = 0; iNum < method.Count; iNum++)
{
while (iNum == (int)blockEnds.Peek())
{
currentBlock = currentBlock.Parent;
blockEnds.Pop();
}
firstBlock = null;
lastBlock = null;
Node thisBlock = null;
while (iNum == nextBlockStart)
{
Block currentBlockOld = currentBlock;
switch (nextBlockType)
{
case BlockType.Try:
currentBlock = new ProtectedBlock();
break;
case BlockType.Catch:
currentBlock = new CatchBlock(nextCatchBlockType);
break;
case BlockType.Finally:
currentBlock = new FinallyBlock(false);
break;
case BlockType.Filter:
currentBlock = new FilterBlock();
break;
case BlockType.FilteredCatch:
currentBlock = new UserFilteredBlock();
break;
}
currentBlock.setParent(currentBlockOld);
blockEnds.Push(nextBlockEnd);
if (thisBlock == null)
{
thisBlock = firstBlock = currentBlock;
}
else
{
thisBlock.Next = currentBlock;
thisBlock = currentBlock;
}
switch (nextBlockType)
{
case BlockType.Try:
tryBlocks.Add(new Segment(nextBlockStart, nextBlockEnd), thisBlock);
break;
case BlockType.Filter:
filterBlocks.Add(new Segment(nextBlockStart, nextBlockEnd), thisBlock);
break;
case BlockType.Finally:
case BlockType.Catch:
{
Segment tryBlockKey = FindProtectedBlock(method.EHClauses, nextBlockIndex);
ProtectedBlock tryBlock = tryBlocks[tryBlockKey] as ProtectedBlock;
tryBlock.AddHandler(thisBlock as EHBlock);
} break;
case BlockType.FilteredCatch:
{
Segment tryBlockKey = FindProtectedBlock(method.EHClauses, nextBlockIndex);
ProtectedBlock tryBlock = tryBlocks[tryBlockKey] as ProtectedBlock;
tryBlock.AddHandler(thisBlock as EHBlock);
Segment filterKey = FindFilterBlock(method.EHClauses, nextBlockIndex);
FilterBlock filterBlock = filterBlocks[filterKey] as FilterBlock;
(thisBlock as UserFilteredBlock).Filter = filterBlock;
} break;
}
FindNextBlockStart(method.EHClauses, out nextBlockType, ref nextBlockStart, ref nextBlockEnd, out nextCatchBlockType, out nextBlockIndex);
}
lastBlock = thisBlock;
Instruction i = method[iNum];
switch (i.Code)
{
case InstructionCode.NEG:
case InstructionCode.NOT:
{
head = tail = new UnaryOp(UnaryOpFromCode(i.Code));
/*!*/ head.setParent(currentBlock);
} break;
case InstructionCode.ADD:
case InstructionCode.AND:
case InstructionCode.CEQ:
case InstructionCode.CGT:
case InstructionCode.CLT:
case InstructionCode.DIV:
case InstructionCode.MUL:
case InstructionCode.OR:
case InstructionCode.REM:
case InstructionCode.SHL:
case InstructionCode.SHR:
case InstructionCode.SUB:
case InstructionCode.XOR:
{
head = tail = new BinaryOp(BinaryOpFromCode(i.Code), i.OverflowFlag, i.UnsignedFlag);
/*!*/ head.setParent(currentBlock);
} break;
case InstructionCode.LDC:
head = tail = new LoadConst(i.Param);
/*!*/ head.setParent(currentBlock);
break;
case InstructionCode.LDARG:
head = tail = new LoadVar(args[(int)(i.Param)]);
/*!*/ head.setParent(currentBlock);
break;
case InstructionCode.LDLOC:
head = tail = new LoadVar(locals[(int)(i.Param)]);
/*!*/ head.setParent(currentBlock);
break;
case InstructionCode.LDARGA:
head = tail = new LoadVarAddr(args[(int)(i.Param)]);
/*!*/ head.setParent(currentBlock);
break;
case InstructionCode.LDLOCA:
head = tail = new LoadVarAddr(locals[(int)(i.Param)]);
/*!*/ head.setParent(currentBlock);
break;
case InstructionCode.LDIND:
head = tail = new LoadIndirect(i.TypeBySuffixOrParam());
/*!*/ head.setParent(currentBlock);
break;
case InstructionCode.LDFLD:
{
FieldInfo field = i.Param as FieldInfo;
if (field.IsStatic)
{
head = new RemoveStackTop();
/*!*/ head.setParent(currentBlock);
//remove the object instance when accessing the static field with LDFLD
tail = new LoadField(field);
/*!*/ tail.setParent(currentBlock);
head.Next = tail;
}
else
{
head = tail = new LoadField(field);
/*!*/ head.setParent(currentBlock);
}
} break;
case InstructionCode.LDFLDA:
{
FieldInfo field = i.Param as FieldInfo;
if (field.IsStatic)
{
head = new RemoveStackTop();
/*!*/ head.setParent(currentBlock);
tail = new LoadFieldAddr(field);
/*!*/ tail.setParent(currentBlock);
head.Next = tail;
}
else
{
head = tail = new LoadFieldAddr(field);
/*!*/ head.setParent(currentBlock);
}
} break;
case InstructionCode.LDSFLD:
head = tail = new LoadField(i.Param as FieldInfo);
/*!*/ head.setParent(currentBlock);
break;
case InstructionCode.LDSFLDA:
head = tail = new LoadFieldAddr(i.Param as FieldInfo);
/*!*/ head.setParent(currentBlock);
break;
case InstructionCode.LDELEM:
head = tail = new LoadElement(i.TypeBySuffixOrParam());
/*!*/ head.setParent(currentBlock);
break;
case InstructionCode.LDELEMA:
head = tail = new LoadElementAddr(i.TypeBySuffixOrParam());
/*!*/ head.setParent(currentBlock);
break;
case InstructionCode.LDOBJ:
head = tail = new LoadIndirect(i.Param as Type);
/*!*/ head.setParent(currentBlock);
break;
case InstructionCode.SIZEOF:
head = tail = new LoadSizeOfValue(i.Param as Type);
/*!*/ head.setParent(currentBlock);
break;
case InstructionCode.LDLEN:
head = tail = new LoadLength();
/*!*/ head.setParent(currentBlock);
break;
case InstructionCode.LDTOKEN:
if (i.Param is Type)
{
head = tail = new LoadConst((i.Param as Type).TypeHandle);
}
else if (i.Param is MethodBase)
{
head = tail = new LoadConst((i.Param as MethodBase).MethodHandle);
}
else if (i.Param is FieldInfo)
{
head = tail = new LoadConst((i.Param as FieldInfo).FieldHandle);
}
else
{
throw new ConvertionException();
}
/*!*/ head.setParent(currentBlock);
break;
case InstructionCode.LDNULL:
head = tail = new LoadConst(null);
/*!*/ head.setParent(currentBlock);
break;
case InstructionCode.LDSTR:
head = tail = new LoadConst(i.Param);
/*!*/ head.setParent(currentBlock);
break;
case InstructionCode.STARG:
head = tail = new StoreVar(args[(int)(i.Param)]);
/*!*/ head.setParent(currentBlock);
break;
case InstructionCode.STLOC:
head = tail = new StoreVar(locals[(int)(i.Param)]);
/*!*/ head.setParent(currentBlock);
break;
case InstructionCode.STIND:
head = tail = new StoreIndirect(i.TypeBySuffixOrParam());
/*!*/ head.setParent(currentBlock);
break;
case InstructionCode.STFLD:
{
FieldInfo field = i.Param as FieldInfo;
if (field.IsStatic)
{
head = new StoreField(field);
/*!*/ head.setParent(currentBlock);
tail = new RemoveStackTop();
/*!*/ tail.setParent(currentBlock);
head.Next = tail;
}
else
{
head = tail = new StoreField(i.Param as FieldInfo);
/*!*/ head.setParent(currentBlock);
}
} break;
case InstructionCode.STSFLD:
head = tail = new StoreField(i.Param as FieldInfo);
/*!*/ head.setParent(currentBlock);
break;
case InstructionCode.STELEM:
head = tail = new StoreElement(i.TypeBySuffixOrParam());
/*!*/ head.setParent(currentBlock);
break;
case InstructionCode.STOBJ:
head = tail = new StoreIndirect(i.Param as Type);
/*!*/ head.setParent(currentBlock);
break;
case InstructionCode.CPOBJ:
head = new LoadIndirect(i.Param as Type);
/*!*/ head.setParent(currentBlock);
tail = new StoreIndirect(i.Param as Type);
/*!*/ tail.setParent(currentBlock);
head.Next = tail;
break;
case InstructionCode.DUP:
head = tail = new DuplicateStackTop();
/*!*/ head.setParent(currentBlock);
break;
case InstructionCode.CALL:
head = tail = new CallMethod(i.Param as MethodBase, false, i.HasTail);
/*!*/ head.setParent(currentBlock);
break;
case InstructionCode.CALLVIRT:
MethodInfo callee = i.Param as MethodInfo;
head = tail = new CallMethod(callee, callee.IsVirtual, i.HasTail);
/*!*/ head.setParent(currentBlock);
break;
case InstructionCode.NEWOBJ:
{ ConstructorInfo ctor = i.Param as ConstructorInfo;
if (Verifier.IsDelegate(ctor.DeclaringType))
{
if (Verifier.IsInstanceDispatch(method, iNum))
{
heads[iNum - 1] = tails[iNum - 1] = null;
head = tail = new CreateDelegate(ctor, method[iNum - 1].Param as MethodInfo, false);
}
else if (Verifier.IsVirtualDispatch(method, iNum))
{
heads[iNum - 2] = tails[iNum - 2] = null;
heads[iNum - 1] = tails[iNum - 1] = null;
head = tail = new CreateDelegate(ctor, method[iNum - 1].Param as MethodInfo, true);
}
}
else
{
head = tail = new NewObject(ctor);
}
/*!*/ head.setParent(currentBlock); } break;
case InstructionCode.NEWARR:
head = tail = new NewArray(i.Param as Type);
/*!*/ head.setParent(currentBlock);
break;
case InstructionCode.INITOBJ:
head = tail = new InitValue(i.Param as Type);
/*!*/ head.setParent(currentBlock);
break;
case InstructionCode.ISINST:
head = tail = new CastClass(i.Param as Type, false);
/*!*/ head.setParent(currentBlock);
break;
case InstructionCode.CASTCLASS:
head = tail = new CastClass(i.Param as Type, true);
/*!*/ head.setParent(currentBlock);
break;
case InstructionCode.BOX:
head = tail = new BoxValue(i.Param as Type);
/*!*/ head.setParent(currentBlock);
break;
case InstructionCode.UNBOX:
head = tail = new UnboxValue(i.Param as Type);
/*!*/ head.setParent(currentBlock);
break;
case InstructionCode.CONV:
head = tail = new ConvertValue(i.TypeBySuffixOrParam(), i.OverflowFlag, i.UnsignedFlag);
/*!*/ head.setParent(currentBlock);
break;
case InstructionCode.POP:
head = tail = new RemoveStackTop();
/*!*/ head.setParent(currentBlock);
break;
case InstructionCode.BEQ:
head = new BinaryOp(BinaryOp.ArithOp.CEQ, false, false);
/*!*/ head.setParent(currentBlock);
tail = new Branch();
/*!*/ tail.setParent(currentBlock);
head.Next = tail;
break;
case InstructionCode.BNE:
head = new BinaryOp(BinaryOp.ArithOp.CEQ, false, false);
/*!*/ head.setParent(currentBlock);
tail = new Branch();
/*!*/ tail.setParent(currentBlock);
head.Next = tail;
break;
case InstructionCode.BGE:
if (TypeFixer.IsFloatOrCompatible(i.Stack.Top()))
{
head = new BinaryOp(BinaryOp.ArithOp.CLT, false, !i.UnsignedFlag);
}
else
{
head = new BinaryOp(BinaryOp.ArithOp.CLT, false, i.UnsignedFlag);
}
tail = new Branch();
/*!*/ head.setParent(currentBlock);
/*!*/ tail.setParent(currentBlock);
head.Next = tail;
break;
case InstructionCode.BGT:
head = new BinaryOp(BinaryOp.ArithOp.CGT, false, i.UnsignedFlag);
tail = new Branch();
/*!*/ head.setParent(currentBlock);
/*!*/ tail.setParent(currentBlock);
head.Next = tail;
break;
case InstructionCode.BLE:
if (TypeFixer.IsFloatOrCompatible(i.Stack.Top()))
{
head = new BinaryOp(BinaryOp.ArithOp.CGT, false, !i.UnsignedFlag);
}
else
{
head = new BinaryOp(BinaryOp.ArithOp.CGT, false, i.UnsignedFlag);
}
tail = new Branch();
/*!*/ head.setParent(currentBlock);
/*!*/ tail.setParent(currentBlock);
head.Next = tail;
break;
case InstructionCode.BLT:
head = new BinaryOp(BinaryOp.ArithOp.CLT, false, i.UnsignedFlag);
tail = new Branch();
/*!*/ head.setParent(currentBlock);
/*!*/ tail.setParent(currentBlock);
head.Next = tail;
break;
case InstructionCode.BRTRUE:
head = tail = new Branch();
/*!*/ head.setParent(currentBlock);
break;
case InstructionCode.BRFALSE:
head = tail = new Branch();
/*!*/ head.setParent(currentBlock);
break;
case InstructionCode.SWITCH:
head = tail = new Switch((i.Param as int[]).Length);
/*!*/ head.setParent(currentBlock);
break;
case InstructionCode.BR:
case InstructionCode.NOP:
case InstructionCode.BREAK:
case InstructionCode.LDFTN: // Expecting further delegate construction...
case InstructionCode.LDVIRTFTN: //
head = tail = new DummyNode();
/*!*/ head.setParent(currentBlock);
break;
case InstructionCode.THROW:
head = tail = new ThrowException();
/*!*/ head.setParent(currentBlock);
break;
case InstructionCode.RET:
case InstructionCode.ENDFINALLY:
case InstructionCode.ENDFILTER:
case InstructionCode.LEAVE:
head = tail = new Leave();
/*!*/ head.setParent(currentBlock);
break;
default:
throw new ConvertionException();
}
if (head != null)
{
head.Options["StackTypes"] = i.Stack.Clone() as StackTypes;
}
if (head != tail) //=> head :: BinaryOp, tail :: Branch
//|| head :: LoadIndirect, tail :: StoreIndirect
{
if (head is BinaryOp && tail is Branch)
{
StackTypes stack = i.Stack.Clone() as StackTypes;
stack.Pop();
stack.Pop();
stack.Push(typeof(int));
tail.Options["StackTypes"] = stack;
}
else if (head is LoadIndirect && tail is StoreIndirect)
{
StackTypes stack = i.Stack.Clone() as StackTypes;
TypeEx type = stack.Pop(); //type == S&
stack.Push(type.type.GetElementType());
tail.Options["StackTypes"] = stack;
}
}
if (firstBlock != null)
{
lastBlock.Next = head;
for (Node n = firstBlock; n != head; n = n.Next)
{
n.Options["StackTypes"] = i.Stack.Clone() as StackTypes;
}
head = firstBlock;
if (tail == null)
{
tail = lastBlock; //This may occure what the NOP instruction starts some block
}
}
heads[iNum] = head;
tails[iNum] = tail;
} //for
mainBlock.Next = heads[0];
//Control flow linkage
for (iNum = 0; iNum < method.Count; iNum++)
{
if (heads[iNum] == null)
{
throw new ConvertionException(); //impossible :)
}
Instruction i = method[iNum];
switch (i.Code)
{
case InstructionCode.BR:
case InstructionCode.LEAVE:
tails[iNum].Next = heads[(int)i.Param];
break;
case InstructionCode.RET:
case InstructionCode.ENDFINALLY:
case InstructionCode.ENDFILTER:
case InstructionCode.THROW:
case InstructionCode.RETHROW:
break;
case InstructionCode.BRFALSE: //false
case InstructionCode.BGE: //false
case InstructionCode.BLE: //false
case InstructionCode.BNE: //false
tails[iNum].Next = heads[(int)i.Param];
(tails[iNum] as Branch).Alt = heads[iNum + 1];
break;
case InstructionCode.BRTRUE: //true
case InstructionCode.BEQ: //true
case InstructionCode.BGT: //true
case InstructionCode.BLT: //true
tails[iNum].Next = heads[iNum + 1];
(tails[iNum] as Branch).Alt = heads[(int)i.Param];
break;
case InstructionCode.SWITCH:
tails[iNum].Next = heads[iNum + 1];
Switch node = tails[iNum] as Switch;
int[] alt = i.Param as int[];
for (int j = 0; j < node.Count; j++)
{
node[j] = heads[alt[j]];
}
break;
default:
tails[iNum].Next = heads[iNum + 1];
break;
}
}
//Removing DummyNodes
for (iNum = 0; iNum < method.Count; iNum++)
{
if (heads[iNum] is DummyNode)
{
Node dummy = heads[iNum];
Node[] prev = new Node[dummy.PrevArray.Count];
for (int j = 0; j < prev.Length; j++)
{
prev[j] = dummy.PrevArray[j];
}
for (int j = 0; j < prev.Length; j++)
{
prev[j].NextArray[prev[j].NextArray.IndexOf(dummy)] = dummy.Next;
}
dummy.RemoveFromGraph();
}
}
return(mainBlock);
}
